1. Technical Field
The present invention relates generally to electronic circuits, and more specifically, the invention relates to switched mode power supplies.
2. Background Information
Many types of electronic equipment use varying amounts of power in normal operation. The range of power demanded from a power supply can be extreme, extending for example from a few milliwatts to nearly 100 watts. Large ranges of loading are common in equipment such as printers, digital video disc (DVD) recorders, and other products that require rapid activation of mechanical motion. Typically, a moderate continuous output power is required for a long duration, for example when a DVD disk is spinning continuously or the print head in a printer is moving across a page. However, a maximum or peak output power is usually required for a relatively short duration and infrequently, for example to reverse the direction of a moving printer head or to spin a disk from startup to its rated speed. Equipment to amplify signals that have a large dynamic range, such as music, for example, can demand power that covers a range of several orders of magnitude.
Designers of power supplies for these applications are challenged to provide a wide range of power while conforming to conflicting requirements of efficiency, size, and cost. Power supplies that can deliver the maximum or peak required power often require the use of components that are over rated for the continuous moderate power level. Efforts to meet the requirements for continuous moderate power and short duration peak power from the same power supply usually lead to designs that are larger, heavier, and more costly than necessary if the load range were limited.